Dozens of members of a clan linked to the Maguindanao massacre are reportedly running for elections, sparking outrage in the Philippines.

Media and rights groups say members of the Ampatuan clan, whose leaders are on trial for the massacre in which 58 people died, are candidates in 2013 elections, some for the president's party.

The revelations have caused outrage on the three-year anniversary of the massacre, with critics saying the Ampatuan family's enduring political influence underlined the country's "culture of impunity".

"That some clan members are running under the banner of President (Benigno) Aquino's party is a serious cause for concern because it imparts a damaging message that impunity is alive and well," Human Rights Watch's Carlos Conde told AFP.

Leaders of the Muslim clan, then allied to Aquino's predecessor, Gloria Arroyo, are accused of carrying out the massacre to stop a local rival from filing his candidacy for Maguindanao province governor in 2010 elections.

Andal Ampatuan Snr, the patriarch and then governor of the province, and four of his sons are on trial, accused of planning or participating in the massacre.

A total of 82 people are on trial, many of whom were allegedly members of the Ampatuans' private army.

The Ampatuans, however, deny all charges against them.

The victims of the massacre include 32 media workers who were travelling in a convoy to report on the opposition candidate's attempt to file election papers. The Ampatuans and their gunmen allegedly stopped the convoy and shot everyone dead.

In the aftermath of the massacre, Ms Arroyo was forced to cut political ties with the family, and its power base in Maguindanao, a Muslim-populated province plagued by violence, appeared to have been diminished.

But the National Union of Journalists of the Philippines says 72 members of the clan are running again as candidates in next year's elections, including nine for Aquino's Liberal Party.

They are representing mostly local level positions in Maguindanao, such as town mayor and on government councils.

Without confirming exactly how many Ampatuans were running for the Liberal Party, presidential spokesman Edwin Lacierda defended the decision to recruit them, saying they did not share the same "brand of politics" as the accused.

Meanwhile, the trial drags on with no signs of an end. Lawyers have said it could take years, or even decades, for the proceedings to conclude amid the Philippines' notoriously overwhelmed justice system.

Three witnesses for the prosecution have been killed over the past three years.